Vol. X, No, 10.] Indian Spiders. 413 



[N.S.] 



very closely — much more closely than they do those of the 

 genus Plesiophr ictus. The Thrigmopoeeae are, indeed, distin- 

 guished from them only by the possession of a stridulating 

 organ, sometimes of a very rudimentary nature, between the 

 chelicerae and the coxae of the palp (see pi. xxxi, figs. 1, 2) ; 

 and they appear to represent a further stage in the progressive 

 series of genera which comprises the Indian Ischnocoleae. 



There can therefore, I think, be no doubt that in the 

 Thrigmopoeeae and the Indian Ischnocoleae we have a single 

 line of evolution, related to the Ischnocoleae found outside the 

 Oriental Region only through its most primitive genus Plesio- 

 phrictus. In Simon's arrangement the Indian genera are, it 

 is true, dispersed among genera from other parts of the world, 

 but there is no reason to think that Simon's classification is 

 a natural one. It is based on characters of the same kind as 

 those by means of which he separated the groups of Avicularii- 

 nae defined in the first volume of his "Histoire Naturelle des 

 Araignees," characters which he gladly abandons as diagnostic 

 of groups, in his "Supplement General" at the end of the 

 second volume of that work, saying " J'avais classe ces 

 Araignees a 1' example de Ausserer, presque exclusivement sur 

 des caracteres artificiels et souvent quantitatifs ....". It is 

 unfortunate that characters of greater value seem to be far from 

 numerous in spiders; but it is to be hoped, now the unity of 

 the Indian Ischnocoleae has been pointed out, that some charac- 

 ter of real phylogenetic significance may be found by which they 

 may be separated from Ischnocoleae from outside the Oriental 

 Region. 



The Selenocosmieae have evidently been derived, through 

 forms with a stridulating organ of the rudimentary type 

 found in the genus Neochilobrachys (pi. xxxi, fig 3), from forms 

 without any stridulating organ at all— perhaps, therefore, from 

 the Burmese Ischnocoleae— and they must first have appeared 

 somewhere beyond the Ganges [ , in the countries where all the 

 forms of Selenocosmieae with primitive or transitional (and most 

 of those with the most highly specialized) stridulating organs 

 are found to-day. That the specialized forms found in the 

 Indian Peninsula and Ceylon have entered from across the 



mi 



and have not originated in those countries, is proved by the 

 fact that, although the transitional forms between the primitive 

 Ischnocoleae and the higher Selenocosmieae are all trans- 

 gangetic the Ischnocoleae themselves, which should be the first 

 to suffer from competition with higher forms, are almost entire- 

 ly confined, in the Oriental Region, to Western and Southern 

 India and to Ceylon. 



1 i.e. from the point of vie W of an inhabitant of Calcutta whiclv , 



i ., , . , r -^ ,, •_ .. iu« T> rtM ^oniaT» ciHp! nt the main stream. 



